A known industrial robot includes, for example, a lower arm, an upper arm connected rotatably relative to the lower arm, and a wrist connected rotatably relative to the upper arm, the wrist and the like being rotatable by an actuator (see, for example, Japanese Patent No. 4529456).
In the technique disclosed in Japanese Patent No. 4529456, an actuator (the “R-axis motor 8” in Japanese Patent No. 4529456) that rotationally drives a wrist is attached to a posterior side of an upper arm; specifically, let a side of the upper arm to which the wrist is connected be an anterior side, the actuator is attached to a posterior side. The abovementioned actuator has a rotor shaft extending in a longitudinal direction and the rotor shaft is disposed so as to extend in parallel with the longitudinal direction of the upper arm. The actuator is thus disposed so as to protrude rearwardly from the upper arm.
A device of a type depending on work performed by a robot is disposed on the posterior side of the upper arm. Specifically, if, for example, the robot performs an arc welding job, a feeder that feeds a torch wire to a leading end of the robot is disposed.
In the technique disclosed in Japanese Patent No. 4529456, the actuator is mounted on the upper arm so as to protrude relatively massively toward a rear from the upper arm. This results in, for example, the feeder being offset rearwardly up to a position at which the feeder does not interfere with the actuator. This can increase the entire robot in size and a space requirement for a robot installation.